Head jerks as an aid to meditation

"Sleepiness occurs when the mind becomes dull. At worst we may actually be nodding off to sleep, but there is a more insidious dullness that is harder to work with. When the mind is simply dull we may actually feel that we are meditating quite well because we are not being distracted by thought. The space we are in however, lacks sparkle and presence."

http://ngakma-nordzin.blogspot.com/2011/07/head-jerks-as-aid-to-meditation.html